The technical field of this invention is fluid delivery valves and, in particular, injection valves and nozzles for fuel delivery and the like.
Injection nozzles for fuel delivery, and fluid injection generally, make use of valves which include a large number of parts or electronic control mechanisms that can have a tendency to fail during use. In a conventional or poppet-type injection nozzles, the valve head typically is biased against the valve seat by a spiral wound spring and a number of support elements to retain the spring and poppet head. These complex mechanisms are not only a frequent causes of fatigue failure but they also present structures which are difficult to clean , likely to leak or likely to catch dirt and other contaminants, thereby resulting in nozzle clogging or flow obstruction.
Moreover, spiral wound spring structures are ill-suited for precision control or metering of high rate fluid transfers. This type of spring is typically better suited for long stroke, low force, movements, while many injection applications, such as automotive gasoline or diesel fuel injections, require a short motion, higher force mechanism which can be repeatedly cycled. For example, the opening of a fuel injection valve will typically only involve a valve head displacement of only 20 to 30 thousands of an inch, every 3 hundredth of a second (at 4000 revolutions per minute).
The poppet-type injector responses to a pulse of high pressure fuel or fluid to operate a poppet, and the relatively high weight of the oscillating mass reduces the speed and the frequency with which the injector can open and close, thereby reducing the fuel economy and power output of the engine.
To avoid the problems inherent in valves which are biased by spiral wound springs, various other devices have been tried. For example, many automotive engine designs now rely upon pintle-type valves. Although these valves are more precise and can operate at a higher frequency, they are far more complex and add significantly to the cost of the fuel injection system. Moreover, the possibility of failure is compounded. In this design, a pintle is typically withdrawn to uncover an orifice by electromechanical (solenoid) means. The distance which the pintle moves is predetermined and, consequently, if any part of the nozzle assembly (pintle, orifice, activator, or control device etc.) is affected by wear, dirt, vibration, heat, electronic failure or maladjustment, the nozzle will deliver an incorrect fuel pulse, with a resulting loss of power, fuel economy or both. These factors dictate vigilant maintenance and even with such maintenance can lead to substantial repair or replcement costs.
There exists a need for better injection valves particularly for automotive applications. A simple, robust injection valve for fuel delivery in automotive engines and the like, which could be cycled with minimal risk of failure or maladjustment, would satisfy a long-felt need in the art.